Casing for a watch



FIG. 1 is a top plan view of a casing for a watch showing my new design;

FIG. 2 is a left side elevational view thereof; the right side elevational view being a mirror image;

FIG. 3 is a first end elevational view thereof;

FIG. 4 is a second end elevational view thereof; and,

FIG. 5 is a bottom plan view. 

The ornamental design for a casing for a watch, as shown and described. 